Subject: Re: SDL-News: Delays in Channels
Date: Mon Jan 27 1997 - 10:18:05 GMT
The originator of this message is responsible for its content.
-----From Rick Reed TSE <rickreed#tseng.co.uk> to sdlnews -----
Sanjay Chakravarty <sanjay#cadence.com> wrote:
>My conclusion is that SDL88 cannot be used as a universal modeling
>language. It is confined to less critical systems like
>telecommunications only, right?
Wrong! SDL-88 could be used with non-delaying communication between
processes by removing all the blocks and putting all the processes in one
block so that the processes communicate by (non-delaying) signal routes.
Of course, removing the blocks may make the system difficult to understand,
so it is better to use SDL-92 and non-delaying channels. There are several
other advantages in using SDL-92, such as the type based constructs which
aid the re-use of models.
SDL-88 does not actually REQUIRE the delay to be random in channels. The
model is that there will be some (perhaps not measurable!) time between
signal being put into the channel and it being put into the input queue of
receiving process instance. It is possible (in fact it is likely) that the
delay on a particular channel is (more or less) constant. The language just
does not specify the delay (fixed or random) - just that there is one. A
simulator that allows the delay of each channel to be specified, does not
therefore conflict with SDL-88.
The signals in one channel are always kept in order, as pointed out by
There is a good case for additional attributes on delaying channels and
also timing of transitions between states so that performance can be more
accurately modelled. This would produce a "timed SDL", a subject of further
study. Your views would be a useful input to SDL community.
Rick Reed, TSE Limited
13 Weston House, 18-22 Church Street
Lutterworth Leicestershire LE17 4AW United Kingdom
Tel +44 14 55 55 96 55; Fax +44 14 55 55 96 58
P.S. I am please to see sdlnews being used for this discussion.
-----End text from Rick Reed TSE <rickreed#tseng.co.uk> to sdlnews -----
For help, email "majordomo#sdl-forum.org" with the body of your email as:
or (iff this does not answer your question) email:
This archive was generated by hypermail 2a23 : Sun Jun 16 2013 - 10:41:39 GMT